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Methane ending up in water

Geologist links gas to Silt-area drilling

Increasing natural gas development south of Silt and Rifle is resulting in more gas from drilling showing up in domestic water wells, a geologist says.

Most of the highest concentrations of methane in water appear to be in the Divide Creek area south of Silt, where gas contaminated surface waters in 2004, Geoffrey Thyne told Garfield County commissioners Monday.

Thyne is a geology professor at the Colorado School of Mines and University of Wyoming. He was asked by the county to analyze the results of the second part of a hydrogeological study being conducted for the region south of Rifle and Silt, where there are now about 1,000 gas wells.

The study is being conducted with funds generated when the state fined EnCana Oil & Gas (USA) $371,200 for the 2004 gas seep from one of its wells at West Divide Creek.

Thyne said the study results also show as much as 6 percent of the water in some domestic wells is produced from gas-bearing underground formations during drilling by energy companies.

None of the study’s results of water well testing showed any levels of benzene or other drilling-related contamination requiring regulatory action. Methane in water isn’t regulated and the gas vents away through bubbling once it reaches a certain concentration, Thyne said.

However, the gas can lead to explosions if it is allowed to build up in enclosed areas, which could happen if a domestic water system includes holding tanks in a basement, he said.

The county plans to notify water well owners of the test results.

Thyne said all gas wells leak a little, and some of that gas will reach domestic water supplies. He believes geological faulting in the Divide Creek area helps explain the increased levels of methane in domestic water there.

He said he disagrees with the Colorado Oil and Gas Conservation Commission, which contends that some methane that appears to come from natural gas production in the area instead is originating from biological sources. If so, there would be signs of carbon dioxide resulting from microbial oxidation, he said. The COGCC could not be reached for comment Monday.

EnCana spokesman Doug Hock said some natural gas in the Divide Creek area originates close to the surface rather than from energy production.

He said EnCana is confident that new state drilling procedures in place in the Divide Creek area are protecting domestic water from natural gas development.